Lukas, I only got it half working.
I created a query parameter "user_id" in the URL settings of the member list page.
In the repeater loop of the users, I assigned the respective user_id correctly from the item and set up a click event on the button to navigate to the /profile page. That part works.
But when the /profile page is opened, the ?user_id is empty. Sorry, I don't understand where the mistake is.